Skoon frequently receives inquiries from customers seeking clarity on clean energy setups. While it’s Skoon and Skoon’s suppliers’ job to ensure that clean energy systems are designed and installed correctly, it is crucial for you as a user to understand what’s going on.
To facilitate this understanding, our energy experts are providing a glimpse into the inner workings of energy systems. In this blog, we delve into the details of hybrid setups and explain why they represent a significant leap forward from relying solely on fossil-powered setups.
Where some people or industries are just starting to explore clean energy solutions for their projects, others may already be working with the systems most of their careers. Therefore, the first part of this blog explains the concept of hybridisation and its benefits in general terms. The second part contains a deep dive in this technology set-up for the readers that want to know more!
Let’s get to it:
In the energy transition, full electrification is the goal. Many companies start with the first step: going hybrid. We start with why adding a battery system to a diesel generator is beneficial in the first place:
- Run the generator at optimal loads: most energy users, e.g., film projects, have spiky energy profiles throughout the day. Variances in load causes inefficiency in engines, increase fuel consumption and increase the need for maintenance. By using batteries alongside the generator, we can balance the load on the generator more effectively. The batteries provide all the electricity, allowing the generator to only run at its most efficient level when the battery needs charging.
- Idle Time and Part load optimisation: diesel generators burn a lot of fuel when they’re idling. On loads that are very low, fuel combustion is less efficient due to lower temperatures in the engine. This results in higher emissions and more dirt formation inside the engines. Newer generators, like Stage V generators, will not even run on low loads without breaking down. With hybrid setups, we can use the batteries to power electrical loads during idle and low periods, so the generator can be turned off. This reduces fuel consumption and boosts efficiency.
- Transient Response: when the power load changes suddenly, some generators take a while to ramp up or down. This delay can lead to wasted fuel or blackouts. With hybrid systems, batteries can step in quickly to handle the load spikes. This helps prevent fuel wastage, is better for the engine and improves efficiency.
In addition to the above, we should not not forget other more obvious benefits of batteries, such as increased silence and reduction of unhealthy fumes. This benefits the working environment on a film set or inner-city construction sites.
To sum it all up, hybridising diesel generators with mobile batteries is a good first step to boost efficiency, save fuel, increase silence, create a healthy environment and reduce emissions. By optimising load balancing, reducing idle time, we create a more sustainable and cost-effective power solution. So, which of your generators can we help hybridise? Let out energy experts help you review that data via Skoon’s platform and take your next steps in your clean energy journey!
Contact our energy experts here if you have any questions!
Want to dig deeper into the concept? Read more below!
Does this sound interesting and do you want more technical information on how this works? Read further to obtain in-depth knowledge of the issues with diesel generators and how hybridising generators help avoid these. Let’s look at the three issues with diesel generators in detail:
- Load Variation: load variation is the main issue with diesel generators, it refers to the changes in the power demand over time. Diesel generators are designed to operate at a certain rated power output, but they often face fluctuating loads that can be lower or higher than their optimal point. This can cause problems such as poor fuel efficiency, increased wear and tear, and reduced lifespan. To cope with load variation, diesel generators need to adjust their output by changing their speed and fuel injection. However, this process is not instantaneous and can result in voltage and frequency deviations that can harm sensitive loads. Load variation is closely related to Part load and transient response issues in the way that these topics are main contributors to the inefficiency of a variating load.
- Idle time and Part Load Optimisation: as mentioned, idle time and Part load optimisation explain why diesel generators operate poorly on low and idle loads. Diesel generators are mostly idling to reduce their transient times. It ensures the engine is already running which reduces the time it takes to start the engine; the power output however is often not needed when generators are idling. This results in fuel being burned, while no or limited power is used. Next to wasting fuel this has a few negative effects on diesel engines. Idle time can lead to wet stacking. During these light load conditions, the engine does not generate enough heat to reach the optimum temperature required for efficient combustion. Consequently, the unburned fuel can condense and build up in the exhaust system, forming a sticky residue commonly referred to as “wet stack.” Wet stacking can have several negative effects on the engine’s performance. It can cause reduced fuel efficiency, decreased power output, increased carbon deposits in the engine components, and increased wear on the exhaust system. The buildup of unburnt fuel in the exhaust can also clog the diesel particulate filter (DPF), leading to potential maintenance issues.
Part load issues are closely related to idle times, the same issues with wet stacking occur and the output of energy per liter diesel is lower than running on optimal loads. The Specific Fuel Curve (or Brake Specific Fuel Consumption – BSFC curve) describes the ratio between energy output of an engine vs the amount of fuel used. This curve helps us understand and improve the efficiency of diesel generators. See the curve below:
Figure 1 – Typical SFC-curve of a Diesel generator
The line shows the inefficiency on the lower end, with higher relative fuel consumption at low loads. The sweet spot is around 80% where efficiency is highest and fuel consumption per kWh is the lowest. While every generator has a unique SFC due to differences in the mechanical parts that translate in different efficiencies over the curve, they do all follow the same trendline and are in a predictable range. By understanding this Curve predictions about fuel usage can be made based on an energy profile. Also, optimizations can be achieved by creating a hybrid set-up where the diesel generator can run at its most efficient load on the SFC.
- Transient response: transient response refers to the ability of the diesel generator to respond to sudden changes in the load. Diesel generators have a limited ramp rate, which is the speed at which they can increase or decrease their output. This is due to its inertia and mechanical limitations, which can affect its performance and stability. When faced with a large step change in the load, such as when a motor starts or stops, diesel generators may not be able to adjust their output quickly enough. This can result in voltage and frequency dips or spikes that can harm sensitive loads. Next to unstable power, the fuel consumption is affected by the response time of generators. With sudden peaks a lot of energy is lost in increasing the torque and inertia in the generator to ramp up the speed of the engine needed to deliver the required power. Sudden drops in the power profile will cause the generator to have more energy output left, due to the torque left in the engine which is not fully used by the demand that suddenly needed less power. Power generation in batteries comes from an electrochemical process, meaning these peaks and drops can be handled instantly with almost no losses. Therefore, letting a battery supply the power to profiles with a lot of peaks, increases the efficiency of the set-up.
In conclusion, load variation, idle time, part load optimization, and transient response are significant factors affecting the efficiency and performance of diesel generators. Load variation leads to issues such as poor fuel efficiency and increased wear and tear. Idle time and part load optimization result in fuel wastage, wet stacking, decreased power output, and maintenance issues. Transient response limitations can cause voltage and frequency fluctuations and affect fuel consumption. To improve efficiency, understanding the specific fuel curve and optimizing load conditions can be beneficial. Additionally, integrating batteries to handle sudden load changes can enhance overall efficiency in power generation.
Please reach out to one of our experts if you want to learn more or spar about the topic!
Scientific background:
Several scientific findings highlight the significant improvements in fuel efficiency and performance achieved through hybrid power generation systems. Test results conducted by Kersey et al. (2018) demonstrate fuel efficiency enhancements of over 40% at low loads and over 60% at very low loads. Kusakana and Vermaak (2013) further emphasize the economic, technical, and environmental benefits of hybrid diesel generator (DG) – battery systems for off-grid rural applications. They report reductions in net present costs, cost of energy produced, capacity shortage, fuel consumption, breakeven grid extension distance, and pollutant gas emissions. Notably, the fuel consumption per kilowatt-hour on 75% of the generator is only half that of the fuel consumption per kilowatt-hour on 30%. Furthermore, Kiray et al. (2021) highlight the increased feasibility of hybrid DG/Li-ion battery systems and the potential for cost savings under specific conditions. Their economic analysis reveals that the addition of a Li-ion battery to a DG can pay for itself within 2.5 to 4 years. Additionally, the study identifies additional savings resulting from the reduction in the working time of the DG, potentially postponing the investment in a new DG and yielding profits amounting to approximately 40% of the fuel savings. These findings collectively demonstrate the significant advancements and benefits associated with hybrid power generation systems, encompassing enhanced fuel efficiency, reduced costs, and environmental impact mitigation.
References:
Kersey, J., Sprengel, M., Babbitt, G., & Johnson, T. (2018). Hybrid Power Generation for Improved Fuel Efficiency and Performance. Czero, Inc., Fort Collins, CO, USA.
Kusakana, K., & Vermaak, H. J. (2013). Hybrid Diesel Generator – battery systems for offgrid rural applications. In 2013 IEEE International Conference on Industrial Technology (ICIT) (pp. 839-844). Cape Town, South Africa: IEEE. doi: 10.1109/ICIT.2013.6505781.
Kiray, V., Orhan, M., & Chijioke, J. N. (2021). Significant Increase in Fuel Efficiency of Diesel Generators with Lithium-Ion Batteries Documented by Economic Analysis. Energies, 14(21), 6904. doi: 10.3390/en14216904.
